Gerald D. Klee, a retired psychiatrist and LSD expert who participated in experiments with the hallucinogenic drug on volunteer servicemen at U.S. military installations in the 1950s, has died. He was 86.

In 1975, Klee made headlines when he confirmed reports that the University of Maryland School of Medicine's Psychiatric Institute had been involved in secret research between 1956 and 1959, when hundreds of soldiers were given LSD, or lysergic acid diethylamide.

He said that in addition to LSD, the Army was experimenting with other hallucinogens as part of its chemical weapons research program.

Klee said the Army had negotiated a contract in 1956 with the University of Maryland's Psychiatric Institute to conduct physiological and psychological tests on the soldiers.

"A large proportion of the people who have gotten involved in research in this area have been harebrained and irresponsible — Timothy Leary being the most notorious example — and a lot of the stuff that has been published reflects that," Klee told the Baltimore Evening Sun in 1975.

"We didn't have any axes to grind, and the university's role was to conduct scientific experimentation," he said. "The interests of the University of Maryland group were purely scientific, and the military was just there."

Klee said soldiers from military posts around the country were brought to the Edgewood Arsenal and Aberdeen Proving Ground installations in Maryland to participate in experiments involving various drugs and chemical warfare agents, of which the hallucinogens were a small part.

"They were mostly enlisted men — there were a few commissioned officers — but they were mostly unlettered and rather naive," Klee said. "Now the people knew they were volunteering, the bonus was leave time — seeing their girlfriends and mothers and that kind of thing. They had a lot of free time, and most of them enjoyed it."

Klee said he and his colleagues from the university tried to explain to the volunteers what to expect.

"They were told it was very important to national security," he said in the Evening Sun interview.

Before the experiments commenced, Klee experimented with LSD.

"I figured that if I was going to study this stuff, then I've got to experience it myself," he told the newspaper. "I felt obliged to take it for experimental reasons and also because I didn't think it would be fair to administer a drug to someone else that I hadn't taken myself."

The LSD was slipped into cocktails at a party in the soldiers' honor. While this approach garnered criticism, Klee said the Army and civilian researchers acted responsibly.

"I was there and I didn't like it, but thought I might be of help to the victims," Klee told the Washington Post in the 1975 interview.

The civilian team quickly learned about those who had experienced "bad trips." He said he did not know of any lasting ill effects on the soldiers but added that university researchers followed the cases only during their month stay at Edgewood.

"What the Army did after that, I don't know. I've given many hours thought to that. I wish I did know," he said in the interview.

"I think he felt unease about this," said a son, Kenneth A. Klee, an editor and writer.

In an email, the younger Klee wrote that his father and his colleagues accepted the military money because they thought it was "important science." He added that because they were World War II veterans and the nation was mired in the Cold War, it "didn't seem unreasonable."

"I do know my dad did his best to do right (and conduct real science — the two were closely linked for him) and that he disapproved of the unethical acts he witnessed. Hence his willingness to be vocal on the subject a few years later," his son wrote.

In 1975, the Army admitted that it had administered LSD to nearly 1,500 people between 1956 and 1967.

Klee later led an unsuccessful effort to persuade President Nixon to renounce the use of LSD as a chemical weapon.

Gerald D'Arcy Klee was born Jan. 29, 1927, and raised in Brooklyn, N.Y. He graduated from high school in 1944, then enlisted in the Army and served in Paris with the Office of Liquidation until being discharged in 1946.

After earning a bachelor's degree in 1948 from McGill University, he graduated in 1952 from Harvard Medical School.

He interned from 1952 to 1953 at the U.S. Public Health Hospital on Staten Island, N.Y., and from 1954 to 1956 completed a residency in psychiatry at Johns Hopkins University and the Veterans Hospital at Perry Point, Md.

From 1959 to 1967, he was director of the Division of Adult Outpatient Psychiatry at the University of Maryland, and served in a similar capacity at Temple University from 1967 to 1970.

Klee also was a medical educator who taught at the University of Maryland, Temple and Johns Hopkins and maintained a private practice until retiring in 2000.

Klee's four marriages ended in divorce. He is survived by two sons, three daughters, a brother and 11 grandchildren.